Spaced Metallic Tyre Cord Structure for Adhesion and Corrosion Resistance

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Solution Overview

Problem

Conventional metallic reinforcing cords in vehicle tires face issues with corrosion, adhesion to elastomeric material, and structural integrity due to uneven distribution and close proximity of metallic wires, leading to cutting forces and potential fatigue cracks.

Innovation Solution

The metallic reinforcing cord features a helical geometry with spaced metallic wires, ensuring a minimum mutual distance greater than three times the wire diameter, enhancing elastomeric material penetration and adhesion, and providing a more homogeneous distribution for improved rigidity and resistance to cutting forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If metallic wires are placed close together in conventional reinforcing cords, then the cord structure is compact and easier to manufacture, but adhesion to elastomeric material is poor and corrosion risk increases

Engineering Contradiction:
Improvecompact cord structureVSAvoidadhesion and corrosion resistance
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The reinforcing cord is segmented into discrete metallic wire elements spaced apart from each other, rather than forming a continuous compact bundle. This segmentation allows elastomeric material to penetrate between individual wires, improving adhesion while maintaining structural integrity through the distributed arrangement of wires along the cord length.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Elastomeric material serves as an intermediary substance that fills the spaces between spaced metallic wires. This intermediary material provides adhesion between the metallic wires and the surrounding tire structure, while also protecting the wires from corrosion by creating a barrier against moisture and environmental factors.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Strength

If metallic wires are uniformly distributed in reinforcing cords, then structural integrity and rigidity are improved, but cutting forces and fatigue crack development increase

Engineering Contradiction:
Improvestructural integrity and rigidityVSAvoidcutting forces and fatigue cracks
Core Design Contradiction:
StrengthVSObject-affected harmful factors

Solution Approach 1:

The reinforcing cord exhibits local quality variations through its helical geometry, where wire density and spacing change along the length of the cord. This allows certain regions to provide enhanced rigidity and structural support while other regions with greater spacing reduce stress concentration and minimize the development of cutting forces and fatigue cracks under dynamic loading conditions.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The metallic wires are arranged in a helical (curved) geometry rather than straight parallel configurations. This curvature distributes mechanical stresses more evenly along the wire length, reducing stress concentration points that would otherwise initiate cutting forces and fatigue cracks, while maintaining the necessary rigidity for structural support.

Inventive Principle:
Principle #14Spheroidality (Curvature)

3Ease of manufacture

If elastomeric material penetration between metallic wires is limited, then manufacturing is simpler, but adhesion is poor leading to reduced structural integrity

Engineering Contradiction:
Improvesimple manufacturing processVSAvoidadhesion and structural integrity
Core Design Contradiction:
Ease of manufactureVSStrength

Solution Approach 1:

The spacing between segmented metallic wires naturally creates channels and pathways that facilitate elastomeric material penetration during the tire manufacturing process. This segmentation eliminates the need for complex manufacturing steps to ensure adhesion, as the material flow is inherently promoted by the spaced wire arrangement.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The reinforcing cord structure functions as a porous arrangement with intentional void spaces between metallic wires. These pores or voids are designed to be filled by elastomeric material during manufacturing, creating strong adhesive bonds without requiring complex processing, thereby simultaneously achieving good adhesion and manufacturing simplicity.

Inventive Principle:
Principle #31Porous materials

Data Source

PatentEP4217211B1Metallic reinforcing cord for tyres for vehicle wheels and tyre comprising said metallic reinforcing cord
Publication Date: 2026.02.11 PIRELLI TYRE SPA
  • EP4217211B1 patent drawingFigure 1
  • EP4217211B1 patent drawingFigure 2
  • EP4217211B1 patent drawingFigure 3~3a

AI summary

The invention relates to a metallic reinforcing cord (10) for tyres for vehicle wheels, comprising from two to ten metallic wires (11) twisted together with a twisting pitch (P) and each having a predetermined diameter. In at least some cross sections of the metallic reinforcing cord (10), at least two of said metallic wires (11) are arranged to a minimum mutual distance greater than, or equal to, 2.5 times the predetermined diameter.